Spark plug for high compression engines



NOV- 6, 1934- H. RABEzzANA 1,979,999

SPARK PLUG FOR HIGH COMPRESSION ENGINES Filed Jan. 20, 1934 PatentedNov. 6, 1934 4 UNITED STATES PATENT OFFICE Hector Babczzana, Flint,Mich., assignor to General Motors Corporation, Detroit, Mich., acorporation of Delaware Application January 20, 1934, Serial No. 707,459

`6 Claims. (Cl. 12S-169) My invention relates to spark plugs forinternal combustion engines, and the object thereof is to provide aspark plug wherein the grounded electrode thereof is so arranged that itwill be more effectively cooled than heretofore.

Another object of my invention is to provide certain features associatedwith the insulating member of the plug whereby the heating thereof whenthe plug is in use is greatly reduced; and a further object is toprovide improved means for adjusting the spark gap between the groundedand insulated electrodes, and for insuring that the length of said gapafter the insulating member has been removed for inspection andcleaning, shall be the same when the parts are reassembled that it wasbefore the insulator was removed, thus maintaining an unchanged lengthof spark gap Vnotwithstanding repeated removals and replacements of theinsulating member.

With the above and other objects in view as will hereinafter appearmyvinvention consists in the spark plug illustrated in its preferredform in the accompanying drawing, and hereinafter described and claimed;and in such modifications and variations thereof, within the scope ofthe concluding claims, as will be obvious to those skilled in the art towhich my invention relates.

In the drawing:

Figure 1 is a view showing a section upon a vertical plane of a sparkplug made in accordance with my invention, certain parts of an enginehead being also shown.

Figure 2 is a view showing a section upon a horizontal plane indicatedby the line 2 2, Figure 1, looking down.

Figure 3 is a similar view taken upon a plane indicated by the line 3 3,Figure 1.

Figure 4 is a view taken upon a vertical plane as in Figure 1, butshowing my improved spark plug modified as to some of its features.

Figure 5 is a view showing a section on a horizontal plane indicated bythe line 5 5, Figure 4, looking down. Y

Referring to the drawing, the cylinder head, which enters into theformation of a spark plug in accordance with my invention, has the usualinner and outer walls and an intervening space 10 which contains acooling liquid, and said head may be either integral with an internalcombustion engine cylinder or formed separate therefrom and securedthereto by the usual holding bolts. Said head has an internally threadedannular part 11 extending upward from the top wall thereof; and arrangedwithin this part and held therein by an externally threadedbushingwherein the insulating member is permanently assembled within ahollow metallic shell or casing. A circular recess or seat 17 in thehead supports the shell 13 the lower end of which lits closely withinsaid seat, but within which seat the shell is angularly adjustable; aholding washer 18 being interposed between the lower end of the bushing12 and an annular shoulder 19 adjacent the lower or inner end of theshell, to thereby hold the shell in place and force its lower endagainst the seat 17 as will be appreciated. The washer 18 has aprojection 21 which extends into a groove 22 within the projecting part1l so that the screwing of the holding nut or gland 12 into theprojection to hold the shell against the seat 17 will not rotate theshell.

The grounded electrode is shown as in theform of a smaller projectingpart 23 extending from an enlarged threaded part or base 24 which screwsinto a threaded electrode passage in a properly shaped portion of theinner wall of the head; and the insulated electrode 25 extends through apassage in the insulating member 14 as is usual.

The lower end 26 of the shell 13, see Figure 3, is preferably madeeccentric to the upper part which holds the insulator, so that angularmovement of the same will vary the length of the spark gap between theelectrodes 23, 25. If before the shell is removed for cleaning the innerend of the insulator, or for any other purpose, the position of theshell is marked as by marking upon the same and washer 18 after removingthe gland nut 12, then if in reassembling the parts the shell or sleeveis positioned as indicated by the marking, the length of the spark gapwill obviously be the same as before the shell was removed.

A washer 27 is commonly placed beneath the head of the groundedelectrode and b`y selecting washers ofdiflerent thicknesses the positionof the inner end thereof may be varied and an average length of sparkgap thus provided, to be thereafter more definitely determined by theadjusting features provided by the eccentric lower end 26 of the shelland the seat 17 into which it extends.

In theV form of my invention illustrated in Figures 4 and 5 the shell orsleeve 28 is concentric as regards all parts thereof, and the groundedelectrode 29 has an enlarged threaded part 30 which is adjustable in athreaded passage in the inner wall of the head; and adjustment of thespark gap is secured by the use of washers 31 of diierent thicknesses,or by compressing such a washer more or less if the washer is of thetype which may yield to a certain degree. In both forms a screw drivermay be inserted through in line with the grounded electrode, and openingis normally closed by a plug 32, to thereby adjust A the groundedelectrode.

Caps 33 and 34 of insulating material diiering somewhat in form in thetwo embodiments of my invention illustrated and hereinbefore describedare provided to protect the upper ends of the insulators, and theconnections between supply cables 35 and 36 and the central electrodes,from the weather, as the plug herein disclosed is designed especiallyfor use with outboard motor engines for boat propulsion; but theseprotecting caps are not claimed in this present application.

In both forms of my invention the enlarged outer threaded parts of thegrounded electrodes provide a metal to metal contact between them andthe inner head wall of large area, which facilitates a rapid owof heatto the wall; and the fact that the cooling liquid is in direct contactwith the head wall about the electrodes and with the outer ends of theelectrodes themselves secures a rapid dissipation of heat from them, andprevents them from becoming overheated when the engine is in operation.The insulating member also is kept at alower temperature than wouldotherwise be the case because of the metallic path provided by the lowerend 26 of the shell 13, which fits closely within an annular recess inthe comparatively cool top wall of the head, the parts being in directmetal to metal contact with one another; so that heat which wouldotherwise ow to the shell and insulator is for the most part divertedthrough the lower end of the shell and to the cool head wall, andexcessive heating of the upper part of the shell and the insulatortherein is avoided. This ow of heat to comparatively cool parts insteadof to the upper part of the shell 13 and to the insulator 14 is furtherfacilitated by contact between the washer 18 and the shoulder 19, andbetween the washer and gland nut 12, thus providing a second metallicpath to the comparatively cool head and which to a degree is independentof the path provided by the lower end 26 of the shell as hereinbeforeexplained.

Having thus described and explained my invention I claim and desire tosecure by Letters Patent:

1. In a spark plug and in combination with a cylinder head having aninternal cooling liquid space, and an internally threaded annular part;'a hollow shell; an insulator assembled within said shell and extendinginto a space containing a combustible mixture to be ignited; aninsulated electrode extending through said insulator and -into sparkingrelation with a grounded electrode;

an externally threaded bushing within said annular part and spaced apartfrom the shell aforesaid; means located adjacent the inner end of saidshell and through which said bushing acts'` to hold said shell in placewith its inner end in direct contact with said head; and a groundedelectrode arranged in sparking relation with the inner end of saidinsulated electrode, and a part of which grounded electrode is in directcontact with cooling liquid within said cooling liquid space.

2. In a spark plug and in combination with a cylinder head having aninternal cooling liquid space, and an internally threaded annular part;a hollow shell; an insulator assembled within said shell and extendinginto a space containing a combustible mixture to be ignited; aninsulated electrode extending through said insulator and into sparkingrelation with a grounded electrode;

an externally threaded bushing within said annular part and spaced apartfrom the shell aforesaid; an annular shoulder adjacent the lower end ofsaid shell; a Washer engaging said shoulder and with which the lower endof said bushing engages to hold said shell in place, with its inner endin direct contact with said head; and a grounded electrode arranged insparking relation with the inner end of said insulated electrode, and apart of which grounded electrode is in direct contact with coolingliquid within said cooling liquid space.

3. In a spark plug and in combination with a cylinder head having aninternal cooling liquid space, an internally threaded annular part, anda circular recess adjacent the lower end of said annular part; a hollowcylindrical shell the lower end of which fits Within said recess; aninsulator within said shell and extending through the lower open endthereof; an insulated electrode extending through said insulator andinto sparking relation with a grounded electrode; an externally threadedbushing within said annular part; means located adjacent the inner endof said shell whereby said bushing acts to hold said shell in place,with its lower end within the recess aforesaid; and a grounded electrodeassembled with the cylinder head and arranged in sparking relation withthe inner end of said insulated electrode.

4. In a spark plug and in combination with a cylinder head having aninternal cooling liquid space, an internally threaded annular part, anda circular recess within and below the lower end of said annular part; ahollow cylindrical shell having an eccentric lower end of circular formtting within said recess; an insulator within said shell; an insulatedelectrode extending through said insulator and into sparking relationwith a grounded electrode; an externally threaded bushing within saidannular part and spaced apart from the shell aforesaid; means adjacentthe inner end of said shell and engaged by the lower end of said bushingfor holding said shell in place, with its eccentric lower end within therecess aforesaid; and a grounded electrode assembled with the cylinderhead and arranged in sparking relation with the inner end of saidinsulated electrode.

5. A cylinder head having inner and outer walls, an intervening coolingliquid space, a threaded grounded electrode passage in said inner walland leading into the interior of said head, and an opening in said outerwall arranged in line with said passage; and a threaded groundedelectrode extending through the passage aforesaid and the outer end ofwhich is in direct contact with cooling liquid within said coolingliquid space.

6. A cylinder head having inner and outer walls, an intervening coolingliquid space, a threaded grounded electrode passage in said inner walland leading into the interior of said head, and an opening in said outerwall arranged in line with said passage; and a grounded electrodeextending through said passage and having an enlarged outer threadedpart in direct contact with cooling liquid within the cooling liquidspace aforesaid, and a reduced inner part'extending into sparkingrelation with an insulated electrode.

